Hard Drives not recognized but no problems are said

as of yesturday they were both woking fine however i woke up this morning and niether one of them is recognized by the computer. I go to the hardware administation and it just says they are unknown devices without the yellow question mark. any ideas on how to fix this?

I´ve tried going back to the last restore point but it didnt work. Aswell as i am typing this up I have a little ballon poping up every about 5 sec telling me that one of the devices has had a problem and windows cant recognize it.

Just plug the Master HardDrive in and remove the Slave and any CD/DVD drive

Note: sometimes just unplugging the drives, and the system power cord out.
Then holding in the ON switch for 30secs (dispersing all internal voltage)
Then replugging in the drives and power cord will work.

Both of these drvies are external drives(USB 2.0). Not the internal one. The internal one is just fine oddly enough.

Also when I sart up the computer and look into the BIOS it recognizes them as hard drives. So I think I have narrowed it down to it being a windows problem.

Another small note, when I first went to re-plug in my seagate drive, windows read it but gave me and error saying more or less that windows could not read / write to file f:/$(some random letters i cant remember) could this be the problem

USB ports seem to be the most sensitive areas of computers, and usually the first to show signs of hardware faults.

But I believe this may still be likely to do with software (Drivers and settings)

One option would be to go into Device Manager (Start->Run-> devmgmt.msc) expand the USB device setting and then remove them all (note: any USB devices attached to your computer, including a usb mouse, will stop working)
Restart the computer and allow all the USB found devices to install
Then plug the external USB Hard Drive back in (using the back USB plugs on Desktops)